Make more use of paradoxical_subreg_p

This patch makes more use of the existing paradoxical_subreg_p
predicate and also adds a version that operates on outer and
inner modes.

Some of the affected tests were based on GET_MODE_SIZE rather than
GET_MODE_PRECISION and so the patch could change the result for modes
that have the same size but different precisions.  I think in each
case the change should be a no-op or more correct, since a mode with
precision N bits can't be expected to hold all of a mode with precision
M>N bits.

The patch changes the branch taken in simplify_subreg for modes with
equal precision, but the new form matches the commentary more closely.
Both branches should be equally good in that situation.

2017-08-22  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* rtl.h (paradoxical_subreg_p): Define inline, and add a version
	that takes the outer and inner modes.
	* doc/rtl.texi: Use paradoxical_subreg_p instead of a GET_MODE_SIZE
	comparison as the canonical test for a paradoxical subreg.
	* combine.c (simplify_set): Use paradoxical_subreg_p.
	(make_extraction): Likewise.
	(force_to_mode): Likewise.
	(rtx_equal_for_field_assignment_p): Likewise.
	(gen_lowpart_for_combine): Likewise.
	(simplify_comparison): Likewise.
	* cse.c (equiv_constant): Likewise.
	* expmed.c (store_bit_field_1): Likewise.
	* final.c (alter_subreg): Likewise.
	* fwprop.c (propagate_rtx): Likewise.
	(forward_propagate_subreg): Likewise.
	* ira-conflicts.c (ira_build_conflicts): Likewise.
	* lower-subreg.c (simplify_gen_subreg_concatn): Likewise.
	* lra-constraints.c (curr_insn_transform): Likewise.
	(split_reg): Likewise.
	* lra-eliminations.c (move_plus_up): Likewise.
	(lra_eliminate_regs_1): Likewise.
	* recog.c (general_operand): Likewise.
	* ree.c (combine_reaching_defs): Likewise.
	* reload.c (push_reload): Likewise.
	(find_reloads): Likewise.
	* reload1.c (elimination_effects): Likewise.
	(compute_reload_subreg_offset): Likewise.
	(choose_reload_regs): Likewise.
	* rtlanal.c (subreg_lsb_1): Likewise.
	* simplify-rtx.c (simplify_unary_operation_1): Likewise.
	(simplify_subreg): Likewise.
	* var-tracking.c (track_loc_p): Likewise.
	* emit-rtl.c (byte_lowpart_offset): Likewise.
	(paradoxical_subreg_p): Delete out-of-line definition.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251282

1 files changed, 9 insertions, 11 deletions

diff --git a/gcc/reload.c b/gcc/reload.c
index 8074e54..691c4b9 100644
--- a/gcc/reload.c
+++ b/gcc/reload.c
@@ -1062,13 +1062,12 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
 	  || (((REG_P (SUBREG_REG (in))
 		&& REGNO (SUBREG_REG (in)) >= FIRST_PSEUDO_REGISTER)
 	       || MEM_P (SUBREG_REG (in)))
-	      && ((GET_MODE_PRECISION (inmode)
-		   > GET_MODE_PRECISION (GET_MODE (SUBREG_REG (in))))
+	      && (paradoxical_subreg_p (inmode, GET_MODE (SUBREG_REG (in)))
 		  || (GET_MODE_SIZE (inmode) <= UNITS_PER_WORD
 		      && (GET_MODE_SIZE (GET_MODE (SUBREG_REG (in)))
 			  <= UNITS_PER_WORD)
-		      && (GET_MODE_PRECISION (inmode)
-			  > GET_MODE_PRECISION (GET_MODE (SUBREG_REG (in))))
+		      && paradoxical_subreg_p (inmode,
+					       GET_MODE (SUBREG_REG (in)))
 		      && INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (in)))
 		      && LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (in))) != UNKNOWN)
 		  || (WORD_REGISTER_OPERATIONS
@@ -1170,8 +1169,7 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
 	  || (((REG_P (SUBREG_REG (out))
 		&& REGNO (SUBREG_REG (out)) >= FIRST_PSEUDO_REGISTER)
 	       || MEM_P (SUBREG_REG (out)))
-	      && ((GET_MODE_PRECISION (outmode)
-		   > GET_MODE_PRECISION (GET_MODE (SUBREG_REG (out))))
+	      && (paradoxical_subreg_p (outmode, GET_MODE (SUBREG_REG (out)))
 		  || (WORD_REGISTER_OPERATIONS
 		      && (GET_MODE_PRECISION (outmode)
 			  < GET_MODE_PRECISION (GET_MODE (SUBREG_REG (out))))
@@ -1299,7 +1297,7 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
   if (this_insn_is_asm)
     {
       machine_mode mode;
-      if (GET_MODE_SIZE (inmode) > GET_MODE_SIZE (outmode))
+      if (paradoxical_subreg_p (inmode, outmode))
 	mode = inmode;
       else
 	mode = outmode;
@@ -3137,15 +3135,15 @@ find_reloads (rtx_insn *insn, int replace, int ind_levels, int live_known,
 			  && (WORD_REGISTER_OPERATIONS
 			      || ((GET_MODE_BITSIZE (GET_MODE (operand))
 				   < BIGGEST_ALIGNMENT)
-				 && (GET_MODE_SIZE (operand_mode[i])
-				     > GET_MODE_SIZE (GET_MODE (operand))))
+				  && paradoxical_subreg_p (operand_mode[i],
+							   GET_MODE (operand)))
 			      || BYTES_BIG_ENDIAN
 			      || ((GET_MODE_SIZE (operand_mode[i])
 				   <= UNITS_PER_WORD)
 				  && (GET_MODE_SIZE (GET_MODE (operand))
 				      <= UNITS_PER_WORD)
-				  && (GET_MODE_SIZE (operand_mode[i])
-				      > GET_MODE_SIZE (GET_MODE (operand)))
+				  && paradoxical_subreg_p (operand_mode[i],
+							   GET_MODE (operand))
 				  && INTEGRAL_MODE_P (GET_MODE (operand))
 				  && LOAD_EXTEND_OP (GET_MODE (operand))
 				     != UNKNOWN)))